This invention relates to a vessel opening top inspection apparatus for inspecting presence or absence of a defect at an opening top of a vessel such as a bottle.
One inspection apparatus of the type mentioned has been already proposed by the applicant of the present patent application and is disclosed in Japanese laid-open pat. No. 59-65243. The apparatus comprises a projector for projecting light toward an opening top of a bottle, a single photoelectric transducer element for receiving light reflected from the opening top of the bottle to output an electric signal of a level corresponding to an amount of the light received, bottle rotating means for rotating the bottle to allow light from the projector to be projected over an entire circumference of the opening top of the bottle, an amplifier for amplifying the output signal of the photoelectric transducer element, the amplifier being adjustable with its amplification degree, a memory for storing an output signal of the amplifier for each bottle, operation controlling means for determining an average of data for a predetermined number of last bottles from among data stored in the memory and for adjusting the amplification degree of the amplifier so as to coincide with a predetermined value, and comparing means for comparing output signals of the amplifier for the entire circumference of the opening top of a bottle for inspection and for outputting a defect signal when an extraordinary component of the output signal of the amplifier exceeds a predetermined value.
However, while the apparatus can detect a defect formed on an opening top of a bottle where the defect is a hollow or depression such as a warp or dip finish and a line over finish which is concave at part of a circumference of the opening top of the bottle and will damage the closure of the bottle, such an overpress finish 3 as seen in FIGS. 2 and 3 which is formed to project annularly along an inner circumference of an opening top 2 of a bottle 1 cannot be detected.
Such an overpress finish 3 may be broken and drop into the bottle and mixed with contents when the opening of the bottle is closed with a crown, a threaded cap or the like. Accordingly, the overpress finish is a most significant drawback.